A Piezoelectric-Metal-Cavity (PMC) actuator

A novel piezoelectric-metal-cavity (PMC) actuator has been designed to exhibit a large flexural displacement. This PMC actuator consists of a metal ring sandwiched between two identical piezoelectric unimorphs. The radial contraction of the piezoelectric ceramic is converted into flextensional motion of the unimorph, causing a large flexural displacement in the centre part of the actuator. The metal cavity acts a function of circumferential coupling of the piezoelectric unimorphs. It was found that the effective piezoelectric charge coefficient of the PMC actuator can approach 40,000 pC/N. With its high piezoelectric and electromechanical coupling coefficients, the PMC actuator gives a static displacement 16 μm can be produced under a d.c. driving voltage of ±77 V.